"Glenn Ashmore" skrev i en meddelelse
news:xOlCe.171881$sy6.140027@lakeread04...
I have been making one off patterns molds and parts regularly for the boat
and can tell you what works for me but I don't know what would be
available
where you are. Scandinavia is a big place. I think Denmark and Sweden
have
some good sources for composite materials.

The main problem here seems to be limited availability simply because very
few people do stuff like this at home.. From the sound of the replies I
think I need to stop by one of the local yachtbuilders and see if they will
sell me the materials I need.. The Home Depot clone only has one grade of
cloth ( 300 grams per sq. meter ) and it aint cheap.... Altho: A common
wallpaper type here is woven glass cloth is dirt cheap.. Could I use the
Home Depot clone for the first layer ( the inner layer actually, but this is
the layer that would be visible ) and just use the wallpapergrade stuff for
a "filler" ? I dont need much strength, just need it to be relatively
stiff...

Mold finish: I sand to about 120 and spray on a polyester based tooling
primer called Duratec Surface primer. It is a soft high build polyester
primer. Wet sand from 400 to 1200 then an automotive compound and finally
a
fine polish like McGuire's. Two coats of cake type carnauba based
automotive wax as a base for the mold release.

Sounds reasonably simple... Although I'd need to replace the primer etc. for
something local...

Mold release: PVA is polyvinyl alcohol. A green liquid that dries to a
thin water soluble film. Spray a very light coat as a binder coat. After
about 10 minutes it will be dry enough to spray a wet coat.

Seems I am going to the yachtbuilder again :-)

Glassing: To do a proper job you need several different glass fabrics and
the Home Despot is definitely not toe place to get them. Price is way to
high and you will be lucky to find anything outer than 6 oz plain weave
cloth.

Seems I am going to the yachtbuilder again :-)


Some terminology: "Gel Coat" is a thick surfacing polyester with lots of
solids. It is the surface that you see when you look at most fiberglass
boats. "Cloth" is a plain weave material. It comes in various weights
from
.5 oz/sq yard to 8 oz. and is used to reinforce the surface. "Roving" is
a
very heavy yarn woven into a loose fabric. It is used for strength and
mass. "Mat" is a random oriented fiberglass felt like material used to
fill
the voids in the coarser roving and prevent the weave pattern from
printing
through the gel coat. "Sanding Aid" is a liquid wax additive that is
mixed
with the last coat of polyester resin. Polyester does not cure hard in
the
presence of air. The wax migrates to the surface and forms a shielding
layer to keep air away from the curing resin.

Excellent.. I needed some words here and there :-)

Start with a sprayed on polyester gel coat as soon as the first coat has
flashed off spray on another. You can roll it on but be careful not to
damage the PVA release. Repeat until you have about 30 mills of thickness
and let is cure for an hour or so. Then you can roll on some regular
polyester resin and lay a scrim of 2oz cloth followed by a layer of 6 oz
cloth and a layer of 8oz mat. You want the resin to fully wet out
everything. Next come several layers alternating roving and mat to build
the thickness you need. Cover the last layer of mat with some 6 oz cloth
and seal it with resin with the wax additive..

This was exactly what I was looking for, now I just need to source the
materials and try not to end up spending thousands of dollars in the process
:-)

/peter